The present invention relates to the prevention of infestation or contamination of buildings by insects, and, more particularly, to an apparatus which deters insects from intruding through household-type screens and to an apparatus which deters insects from penetrating greenhouses, food storage facilities, and the like, and to an apparatus which deters termites from infesting and damaging wood structures.
The intrusion of insects into buildings, food products, etc., poses many problems. Insects such as termites and cockroaches are potentially destructive and disease-carrying; moths, flies, bees and mosquitoes bring with them various characteristic problems.
In an effort to meet the challenges posed by the insects, various methods of preventing or reducing insect infestation have been developed. Of the techniques used for prevention and elimination, insecticides are probably the most effective, but require periodic and possibly frequent reapplication to maintain effectiveness. In addition, insecticides are often toxic not only to the target insects, but also to non-targeted insects, plants, animals, and human beings. The use of insecticides is often ineffective when the breeding area of the pests is unknown or inaccessible.
Various attempts have been made to deal with insect intrusion in a non-toxic fashion, including fourth-generation insecticides, which are highly specific to a particular pest. The proper application of such chemicals is characteristically difficult, and a different insecticide is required for each kind of pest. As with less sophisticated chemicals, the application is generally ineffective when the breeding area of the pests is unknown or inaccessible. Moreover, the use of insecticides is in some cases prohibited by law to prevent contamination of underground waters.
Electrical and mechanical devices for the elimination of insects are an alternative or a supplement to chemical sprays, coatings, and traps. Such devices typically lure the insects and subsequently trap and/or kill them. These devices fall far short of providing comprehensive protection against infestation. Not only do they allow the insects free entry into the building, in some cases they exacerbate the problem by attracting more insects.
Many prior art devices employ high voltage systems to electrocute and bum the insect, and require special means of protection. Such devices cause unpleasant odors and are likely to leave an unsightly residue, which is particularly disadvantageous when applied to a screen.
The idea of repelling insects with low voltage is also taught by prior art. U.S. Pat. No. 4,827,874 to Mahan discloses applying a low voltage to conductive strips secured to the side wall of a pet feeding dish to discourage movement up the dish. This device does not, however, provide a fundamental solution for airborne insects, neither does it prevent the insects from entering a building.
In Saunders et al., U.S. Pat. No. 5,007,196, insects are discouraged from getting into a site by applying a low voltage current to a screen at the base of a vertical structure. The insect completes the circuit, and the voltage is such that the insect is repelled but not electrocuted. This invention provides a solution for crawling insects, but not for airborne or jumping pests.
Standard household-type screens, commonly known as 16xc3x9718 mesh screens, provide protection against crawling, jumping, and flying insects. However, such screens are ineffective in preventing the penetration of insects that can penetrate the screen, such as small mosquitoes. Moreover, household screens wear and tear with time, such that even larger insects simply move along the screen until the enlarged opening is discovered. The entire screen is rendered ineffective, requiring the installation of a new unit.
Screens are also used in agricultural applications as a means of protecting crops from intruding insects and from the various associated damages resulting therefrom. Greenhouses are typically fitted with screen in which the openings are xcx9c0.30 mm (50 mesh, ASTM). Screens with larger openings provide ineffective protection. Screens with openings of 0.30 mm provide some protection, but many kinds of insects are small enough to penetrate the openings with facility. For example, Thrips tabaci is an insect that causes significant damage to crops in most areas of the world. Adult Thrips tabaci have a body width of only 0.03-0.05 mm, and have no trouble passing through standard agricultural screens with 0.30 mm openings.
Screens with smaller openings are considerably more expensive. Moreover, the increased screen density negatively impacts the climactic conditions in the protected area, such that both sunlight and ventilation are substantially reduced.
Some growers spray their larger-mesh screens with insecticides to overcome these problems, but without great success.
There is thus a widely recognized need for, and it would be highly advantageous to have, a non-toxic, user-friendly prophylactic device providing inexpensive, comprehensive protection from all types of insects, including flying insects and including tiny insects that normally penetrate household and agricultural screens.
It is therefore an object of the present invention to provide an insect-repelling device and method that prevent all kinds of insectsxe2x80x94crawling, jumping, and flyingxe2x80x94from entering a protected structure.
It is another object of the present invention to provide a protective device that is effective in repelling tiny insects, which normally penetrate ordinary household and agricultural screens.
It is another object of the present invention to provide a method of protection that is non-lethal to the insects such that the deposition of unsightly insect residue is avoided.
It is another object of the present invention to provide an effective protective device that is non-toxic and is harmless to human beings and animals when touched.
Another object of the present invention is to provide such effective protection against intruding insects in an inexpensive fashion, using a system that is simple to operate and can work continuously.
It is another object of the present invention to provide an effective protective device that is effective in repelling tiny insects that normally penetrate ordinary household and agricultural screens, while maintaining and not reducing the amount of sunlight and ventilation.
It is yet another object of the present invention to retrofit standard household screens, such that the function of such screens is substantially augmented without the implementation of an additional system.
Yet another object of the present invention is to provide a device that increases the longevity of standard household-type screens.
According to the present invention there is provided a system for preventing the intrusion of insects and providing a substantially insect-free zone, which comprises a screen, wherein each screen opening is bounded by two conducting elements separated by an insulating medium, and a source of electrical current connected to two conducting elements such that a low-voltage differential is established across boundaries of the opening. When an insect body bridges between conducting elements of opposite charge, the low-voltage differential induces a nervous and muscular reaction in the insect, such that the insect is repelled.
As used herein in the specification and claims section below, the word xe2x80x9cscreenxe2x80x9d refers to a framework with multiple holes, spaces, or perforations, designed to allow the passage of air and/or light and or particles through said holes, spaces, or perforations. The screen as described herein is typically, but not limited to, a network made up of wires or threads running in more than one direction to form a mesh configuration, a framework of parallel or crisscrossed bars, or a plate with multiple perforations.
According to further features in preferred embodiments of the invention described below, the screen is constructed such that the entire screen grid can be activated by connecting a small power source to two conducting, insulated wires on the grid.
In a preferred embodiment, the device is manufactured in a layered, sandwich-type configuration, with conducting material in the top and bottom layers and an insulating material in between. Slits are made in the material, according to standard industrial practice, such that expanded, conducting lath is obtained upon stretching. The top and bottom layers of the device are connected to a low-voltage, low-current power source. The entire perimeter of the openings is electrically-activated, such that a voltage-differential is produced, and insects attempting to penetrate are shocked and repelled.
In another preferred embodiment, the device is layered in a sandwich-type configuration, as described above. Perforations or openings of various geometries (e.g. square, circular, rectangular) are made through the layers according to standard manufacturing practices. The top and bottom layers of the device are connected to a low-current power source. The thickness of the insulating layer is such that an insect attempting to penetrate through an opening must necessarily bridge the gap between positively-charged and negatively-charged layers. The current passing through the body of the insect shocks and repels the insect, thereby inhibiting penetration.